Ethertype conflicts with third-party switches
Some third-party network equipment may use packets with Ethertypes that are the same as the ethertypes used for HA heartbeat packets. For example, Cisco N5K/Nexus switches use Ethertype 0x8890 for some functions. When one of these switches receives Ethertype 0x8890 heartbeat packets from an attached cluster unit, the switch generates CRC errors and the packets are not forwarded. As a result, FortiGate units connected with these switches cannot form a cluster.
In some cases, if the heartbeat interfaces are connected and configured so regular traffic flows but heartbeat traffic is not forwarded, you can change the configuration of the switch that connects the HA heartbeat interfaces to allow level2 frames with Ethertypes 0x8890, 0x8893, and 0x8891 to pass.
You can also use the following CLI commands to change the Ethertypes of the HA heartbeat packets:
config system ha
set ha-eth-type <ha_ethertype_4-digit_hex>
set hc-eth-type <hc_ethertype_4-digit_hex>
set l2ep-eth-type <l2ep_ethertype_4-digit_hex>
end